The invention relates to an endoscope system for observing human tissue that is illuminated with light having a predetermined wavelength. More specifically, the human tissue is illuminated with light having a predetermined wavelength, resulting in the tissue fluorescing at another predetermined wavelength. The fluorescence of the tissue is detected and processed by the endoscope system.
It is known that when human tissue is illuminated by light which has a wavelength of between 400 nm (nanometers) and 480 nm (hereinafter referred to as excitation light), the tissue will fluoresce (glow), thereby producing light having an approximate wavelength between 520 nm and 600 nm. Cancerous human tissue, however, does not fluoresce even if it is illuminated with the excitation light. Therefore, cancer at an early stage, which may not be detected during a normal endoscope observation, can be detected with an endoscope system which illuminates the tissue with the excitation light (i.e., a fluorescence diagnosis endoscope system).
A conventional fluorescence diagnosis endoscope system has an excitation light filter between a light source and a light path of an endoscope, and a fluorescent light filter between an objective optical system and an image receiving element provided at the insertion side of the endoscope. The excitation light filter allows only the excitation light to pass through, and the fluorescent light filter allows only the fluorescent light to pass through. An example of such an endoscope system is disclosed in a Japanese Patent Provisional Publication HEI 4-150845.
Since the intensity of the light produced by the fluorescence of the illuminated tissue is low, it is sometimes difficult to obtain a fluorescent image of the tissue that is sufficiently bright. Therefore, it is difficult to perform the diagnosis accurately.
Further, due to the construction of the conventional fluorescence diagnosis endoscope system described above, only the light produced by the fluorescence of the tissue enters the image receiving element of the endoscope. Thus, the organs or the tissue cannot be observed when the tissue is illuminated with normal light by the same endoscope. In order to examine the organs or tissue using normal light, the endoscope for the fluorescence diagnosis is removed and another endoscope for the normal observation is inserted.
This is both time consuming and disruptive during an examination of a person.
It is therefore a first object of the invention to provide an improved endoscope system which is capable of processing the low intensity of the fluorescent light to obtain a bright image, using the fluorescence diagnosis endoscope system.
Another object of the invention is to provide an endoscope system capable of improving the facility of observation of the person when both the fluorescence diagnosis and the diagnosis with the normal light are performed.
A further object of the invention is to provide an endoscope capable of outputting image signal sufficient to perform diagnosis when the fluorescence image is received.
A still further object of the invention is to provide an endoscope system in which general purpose endoscope is utilized to configure the fluorescence diagnosis system.
A further object of the invention is to provide a video processing unit to which either a general purpose endoscope or an endoscope for the fluorescence diagnosis can be connected.
For the above objects, according to an aspect of the invention, there is provided a fluorescence diagnosis endoscope system used to observe human tissue, the system including a light source for illuminating the human tissue with light having a plurality of wavelength ranges, the human tissue fluorescing in response to illumination with excitation light. The excitation light has a predetermined wavelength range within the plurality of wavelength ranges. The system also includes a pair of image receiving elements, each of the pair of image receiving elements outputting an image signal corresponding to an optical image. An objective optical system for forming optical images of the human tissue is provided on each of the pair of image receiving elements, and a filter for transmitting light produced by the fluoresced tissue is arranged between one of the pair of image receiving elements and the objective optical system. Also included is a device for selecting one of the pair of image receiving elements, a device for processing the image signal output by each one of the pair of image receiving elements, and a device for outputting a video signal output by the selected one of the pair of image receiving elements. With this endoscope system, human image receiving elements. With this endoscope system, human tissue can be observed using a normal image and a fluorescence image without exchanging the endoscope. Therefore, the facility of observing the person can be improved.
The predetermined wavelength of the excitation light is preferably in a range between 400 nm and 480 nm. Further, the light emitted by the fluoresced tissue has a wavelength in a range between 500 nm and 600 nm.
The endoscope system can be constructed such that the light source illuminates the object with red, green and blue light, and the blue light is used as the excitation light. Therefore, another light source for emitting the excitation light is not required.
Alternatively, the light source can be constructed such that a lamp and a plurality of filters respectively transmit light having different wavelengths, with one of the plurality of filters transmitting only the excitation light. For example, the system may be provided with a red, green and blue filter as well as the filter for transmitting the excitation light. Generally the transmission wavelength range of the blue filter is 400 nm-500 nm. The excitation light filter can be a filter having the transmission wavelength range of 400 nm-480 nm. According to this range, the fluorescent light filter can be a filter having a wider transmission wavelength range of 480 nm-600 nm.
According to another aspect of the invention, there is provided an endoscope for receiving fluorescent light emitted by an object including an image receiving element for receiving an image of the object and for outputting an image signal corresponding to the received image. The image receiving element includes a device for amplifying the image signal, an objective optical system for forming the image of the object on the image receiving element, and a device for transmitting light having a predetermined wavelength range to the object for illuminating the object. The object producing the fluorescent light has another predetermined wavelength range, in response to illumination with light having the predetermined wavelength range. A filter is provided between the image receiving element and the objective optical system for transmitting light having the another predetermined wavelength range, and for not transmitting light having the predetermined wavelength range. Therefore, according to this system, even if the intensity of the fluorescent light emitted by the human tissue is relatively low, it can be dealt with a bright fluorescence image can be obtained.
Optionally, the image receiving element comprises an amorphous silicon multi-layer amplified MOS imager.
Alternatively, the image receiving element includes a CCD associated with an image intensifier.
Further, the image intensifier is capable of changing its sensitivity, and the sensitivity is set relatively low when the object emits light having a wavelength range outside the range between 500 nm to 600 nm, while the sensitivity is set relatively high when the object emits the wavelength range between 500 nm to 600 nm. According to a further aspect of the invention, there is provided a fluorescence diagnosis endoscope system including an electronic endoscope for receiving an image of an object to be observed and for outputting an image signal corresponding to the received image. A light source is provided for illuminating the object with light having at least one of a plurality of wavelength ranges. The light source illuminates the object with an excitation light having a predetermined wavelength range, and the object fluoresces in response to illumination by the excitation light. The system also includes a fiber scope for inserting into an instrument channel of the electronic endoscope, the fiber scope having a lens at a tip for converging the light from the object and for transmitting the light through the fiber scope. Also included is an image receiving element for receiving the light transmitted through the fiber scope, and a filter provided between an end of the fiber scope opposite the tip and an other image receiving element, the filter transmits light emitted by the fluoresced object and does not transmit light having the predetermined wavelength range. A device for receiving the image signal output by the image receiving element and outputting a corresponding video signal is also provided.
According to this system, the conventional endoscope only having an image receiving element for the normal image is used, and the fluorescence image can also be observed without exchanging the endoscope.
According to still another aspect of the invention, there is provided an endoscope including a pair of image receiving elements for receiving images and for outputting image signals corresponding to the received images, an objective optical system for forming the images on the image receiving elements, and a device for transmitting light having a predetermined wavelength range to illuminate an object. The object fluoresces in response to illumination with the transmitted light. A filter is provided between one of the image receiving elements and the objective optical system for transmitting light emitted by said fluoresced object and for preventing transmission of light reflected by the object. According to this system, since the endoscope has two image receiving elements for the normal image and for fluorescence image, and the image receiving elements output respective image signals, the normal image and the fluorescence image can be selectively observed without exchanging the endoscope.
According to a further aspect of the invention, there is provided a video processing unit for an endoscope including:
a first and a second image signal processing circuits, each of the image signal processing circuit being capable of receiving an image signal transmitted from an image receiving element of an endoscope, the first and the second image signal processing circuits having different characteristics. Thus, depending on the condition of light which is incident to an image receiving element of an endoscope, the first and the second image signal processing circuit is selectively used.
Optionally, the first image signal processing circuit can receive image signals representative of a plurality of frames corresponding to a plurality of components of light, and output a frame of a color video signal.